Blocking oscillator converters have been used for transferring energy from a vehicle battery to the capacitive storage means in ignition systems because of the capability of high efficiency in this type of converter. Various means have been used to control the power output of the converter such as that shown in applicant's U.S. Pat. No. 3,395,686 which effectively regulates the volt time integral to the converter primary winding to a level selected to charge the energy storage capacitor in a single cycle. This effectively controls not only the voltage on the capacitor, but allows time for the output switching SCR to return to the off state because of the relatively low frequency of the converter. This type of circuitry, however, has the disadvantage that the converter transformer must be relatively large to store the entire required energy in one cycle and thus heavy and expensive. Applicant's U.S. Pat. No. 3,302,130 shows a means of controlling the output voltage of the blocking oscillator by sensing that voltage as reflected to another winding on the oscillator transformer and thus controlling the drive to the blocking oscillator switching transistor. However, the frequency is still limited by the turnoff characteristics of the output SCR and efficiency and capability of operating over a wide range of input voltages are limited by dissipation in the drive circuit of the converter switching transistor.
While the teaching of the previous patents just mentioned have resulted in satisfactory solid state ignition systems, they have not been applied to some applications because of size, weight, or cost.
It is an object of this invention is to produce a solid state ignition system containing a converter operating at a frequency high compared to the required output spark repetition rate and with feedback control to minimize output variations resulting from input voltage variations or engine speed.
It is a further object of this invention to allow the converter to be gated off for a period of time following each output spark to allow the output switching device to turn off.
It is a still further object of this invention to produce a DC to DC converter capable of operating efficiently over a wide range of input and/or output voltages and which is very insensitive to the characteristics of the active devices used therein, which characteristics may change from device to device or with temperature.